1. Field of the Invention
The present invention relates generally to prepreg ribbons. In particular, it relates to prepreg ribbon forms which have non-rectangular architectures.
2. Description of the Related Art
Ribbonized prepreg is used in the automated placement process where ribbons are robotically managed and continually fed onto a tool or part surface and adhered by application of heat and pressure. This automated placement process is particularly sensitive to ribbon material quality when considering low-flow matrix materials. The simultaneous assembly of adjacent ribbons (typically 4 to 34) offers significant advances in the lay-up of composite prepregs. The low-flow matrix materials (which are often high performance) combined with lack of ribbon cross-sectional dimensional integrity, and most importantly, the existence of the standard rectangular cross-section, complicates the automated placement process frequently rendering poor results. Although ribbons are bonded to their vertical neighbor (directly below) satisfactorily, the failure to make quality parts is generally attributed to the poor bonding of adjacent ribbons to each other. Low-flow thermoplastic parts made by using slit prepreg tapes are typically unconsolidated and exhibit excessive porosity and void content. High to moderate-flow matrix prepreg tapes and ribbons generally provide well consolidated, void-free parts. This contrast can be attributed to the correcting melt-flow nature of the high-flow matrix which allows for simultaneous congregation and filament intermingling of neighboring ribbons.
An object of the present invention is to provide a prepreg ribbon having a cross-sectional geometry which promotes intimate lateral contact between adjacent composite tows.
Another object of the present invention is to prepare a composite from the prepreg ribbons having the aforementioned geometry.